The risk of dying from malaria, an infection carried by mosquitoes, increased with age, and the death rate for those over age 65 was 4.6 percent. There were no deaths in children younger than age 5, according to the study published online March 28 in the British Medical Journal.

The researchers also found that tourists were more than nine times more likely to die from malaria than people of African heritage who traveled to see family or friends — 3 percent vs. 0.32 percent.

This decreased death risk among people of African heritage may be due to early exposure to malaria, or to greater awareness of the symptoms and a tendency to seek medical help earlier, the study authors said in a journal news release.

The overall death rate from malaria for people who visited Gambia was especially high (3.9 percent) compared to those who visited other countries in West Africa (0.4 percent). Among tourists, the death rate was 6 percent for those who visited Gambia compared with 1.4 percent for those who visited other West African countries.

Travel to malaria-infected regions is increasing, and the U.K. has one of the highest rates of imported malaria in the world, according to the researchers at the London School of Hygiene and Tropical Medicine and the University of Oxford.

They said doctors need to make travelers aware that malaria is common, possibly fatal and requires early diagnosis. Doctors must stress to travelers the importance of taking anti-malaria drugs and of seeing a doctor immediately if they have a fever when they return home.

Each year, 250 million cases of malaria occur worldwide, resulting in more than 800,000 related deaths, the release said.